1. Field of the Invention
The present invention generally relates to a belt coating material which is applied onto a molding part belt of a belt type continuous casting device, and a method for coating the material onto the belt.
2. Description of the Related Art
With respect to FIGS. 2 and 3, the general construction and operation of a conventional belt-type continuous casting device is explained below. In FIG. 2, the device has a tundish 28, a nozzle 27 at the lower part of tundish 28, a pair of endless belts 21 facing each other and rotating in the opposite directions, and a pair of side dams 23 each comprising a series of combined small copper blocks which rotate together with the belts 21, with dams 23 being clamped between the lateral ends of each belt 21, respectively. The molten steel 30 within the tundish 28 is supplied from the nozzle 27 into a rectangular parallelepiped casting space which is defined by the belts 21 and the side dams 23. The belts 21 and dams 23 are moved at the same speed, and a cast slab 33 having a solidified shell 32 is produced.
FIG. 3 shows a means or mechanism for supplying a coating material onto the surfaces of moving belts 21, in a belt type continuous casting device such as noted above. The pair of metal belts 21 are wound onto pulleys 22, and a molding portion 20 of the casting space is defined by the belts 21 and side dams 23.
Coating devices 24 are disposed above the belts 21, such that the gaps "g" are defined between the tip portions of coating nozzles 25 of these devices and the surfaces of belts 21. Induction heating coils 26 are disposed to face each surface of the ascending portions of belts 21, respectively.
The composition of coating material 41 is described, for example, in Japanese Patent Laid-Open Publication No. HEI-6-226,408. Namely, the material is provided in a slurry state, in which the graphite concentration in the matrix is greater than 20% (preferably, greater than 30%), the concentration "C" of solids in the slurry satisfies C.ltoreq.75-0.4x (where "x" is the graphite concentration in the matrix), the graphite grains are crystalline and have diameters of 50 .mu.m to 500 .mu.m, and the remainder comprises zircon. The coating devices 24 contain such a slurry of coating material.
The coating material 41 is applied onto the belts 21 by the coating nozzles 25 at a predetermined thickness t, while rotating the belts 21, pulleys 22 and side dams 23. The belts 21 and coating material 41 are heated to be dried at a temperature of 120.degree. C. by the induction heating coils 26, and then fed into the molding part 20, followed by the continuous supply of the molten steel 30 from the tundish 28 via injection nozzle 27 into molding portion 20. The cast slab 33 is discharged downward having the solidified shell 32 formed by cooling.
The conventional coating material may not melt even when it comes into contact with the molten steel 30 supplied into the molding portion 20, and an interstitial material (consisting mainly of alumina), which has entered between the cast slab and coating material, is not adsorbed anywhere and remains disadvantageously on the surfaces of the slab.